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Photometric analysis of the eclipsing polar MN Hya

Research in Astronomy and Astrophysics 2018年第7期18卷 11-20页

作者： Qi-Shan Wang Sheng-Bang Qian Zhong-Tao Han Miloslav Zejda Eduardo Fernandez-Lajus Li-Ying Zhu Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming650216China University of Chinese Academy of Sciences Beijing 100049China Department of Theoretical Physics and Astrophysics Masaryk UniversityKotlfirgkfi 2Bmo 611 37Czech Republic Facultad de Ciencias Astron6micas y Geoffsicas Universidad Nacional de La PlataPaseo del Bosque s/n1900La PlataPcia.Bs.As.Argentina Instituto de Astroffsica de La Plata(CCT La plata-CONICET/UNLP) Argentina

As an eclipsing polar with a 3.39 h orbital period, MN Hya was going through a state change when we observed it during 2009-2016. Ten new mid-eclipse times, along with others obtained from literature, allow us to give a new ephemeris. The residuals of a linear fit show that period decreased during the phase of state change, which means angular momentum was lost during this phase. The associated X-ray observation indicates the mass accretion rate was about 3.6 x 10^-9 Mo yr^-1. The period decrease indicates that at least 60% of mass being transferred from the secondary was lost, maybe in the form of spherically symmetric stellar wind. In the high state, the data show the intensity of flickering reduced when the system had a higher accretion rate, and that flickering sticks out with a primary timescale of about 2 min, which implies the position of the threading point was about 30 white dwarf radii above its surface. The trend of light curves for the system in its high state follows that of the low state for a large fraction of the phase interval from phase 0 to phase 0.4 since, starting at phase 0.4, the cyclotron feature is visible, and the primary intensity hump of the light curves near phase 0.7 when the system is in the high state did not appear on the curve when it was in the low state. Those facts contradict predictions of the two-pole model.

关键词： techniques photometric-stars cataclysmic variables eclipsing polars-stars individ-ual （MN Hya）

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A comprehensive and uniform sample of broad-line active galactic nuclei from the SDSS DR7

arXiv

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arXiv 2019年

作者： Liu, He-Yang Liu, Wen-Juan Dong, Xiao-Bo Zhou, Hongyan Wang, Tinggui Lu, Honglin Yuan, Weimin Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100101 China School of Astronomy and Space Science University of Chinese Academy of Sciences 19A Yuquan Road Beijing100049 China Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan650011 China Polar Research Institute of China 451 Jinqiao Road Shanghai200136 China CAS Key Laboratory for Researches in Galaxies and Cosmology University of Sciences and Technology of China Hefei Anhui230026 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming Yunnan650011 China

A new, complete sample of 14,584 broad-line active galactic nuclei (AGNs) at z 38.5- 1044.3erg s-1, and line widths (FWHMs) of 500-34,000 km s-1. The virial black hole masses, estimated from the broad-line measurements, span a range of 105.1- 1010.3Mo, and the Eddington ratios vary from -3.3 to 1.3 in logarithmic scale. Other quantities such as multiwavelength photometric properties and flags denoting peculiar line profiles are also included in this catalog. We describe the construction of this catalog and briefly discuss its properties. The catalog is publicly available online. This homogeneously selected AGN catalog, along with the accurately measured spectral parameters, provides the most updated, largest AGN sample data, which will enable further comprehensive investigations of the properties of the AGN population in the low-redshift universe. Copyright © 2019, The Authors. All rights reserved.

关键词： Surveys

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Reddening of the blr and nlr in agn from a systematic analysis of balmer decrement

arXiv

引用

arXiv 2018年

作者： Lu, Kai-Xing Zhao, Yinghe Bai, Jin-Ming Fan, Xu-Liang Chinese Academy of Sciences KunmingYunnan650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China School of Physics Huazhong University of Science and Technology Wuhan430074 China

We selected an active galactic nuclei (AGN) sample (0 b/Hβb) and narrow-line Balmer decrements (Hαn/Hβn) of 554 selected AGNs. We found that the distributions of Balmer decrements can be fitted by a Gaussian function and give the best estimates of Hαb/Hβb = 3.16 with a standard deviation 0.07 dex, and Hαn/Hβn = 4.37 with a standard deviation 0.10 dex. We inspected the distributions of Hαb/Hβb and Hαn/Hβn in the Baldwin−Phillips−Terlevich (BPT) diagram and found that only narrow-line Balmer decrements depend on the physical conditions of the narrow-line region (NLR). We tested the relationship between Hαb/Hβb and Hαn/Hβn, and found that Hαb/Hβb does not correlate with Hαn/Hβn. We investigated the relationship between Balmer decrements and Seyfert sub-type, and found that only broad-line Balmer decrements correlate with Seyfert sub-type, We also examined the dependency of Balmer decrements on AGN properties, and found that Balmer decrements have no correlation with optical luminosity, but show some dependence on accretion rate. These results indicate that the NLR is subject to more reddening by dust than the broad-line region (BLR). Copyright © 2018, The Authors. All rights reserved.

关键词： Statistics

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GeV-TeV γ-ray energy spectral break of BL Lac objects

arXiv

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arXiv 2018年

作者： Zhong, W. Liu, W.G. Zheng, Y.G. Department of Physics Yunnan Normal University Kunming650092 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

In this paper, we compile the very-highenergy and high-energy spectral indices of 43 BL Lac objects from the literature. Based on a simple math model, ΔΓobs= αz + β, we present evidence for the origin of an observed spectral break that is denoted by the difference between the observed very-high-energy and high-energy spectral indices, ΔΓobs. We find by linear regression analysis that α ≠ 0 and β ≠ 0. These results suggest that the extragalactic background light attenuation and the intrinsic curvature dominate on the GeV-TeV γ-ray energy spectral break of BL Lac objects. We argue that the extragalactic background light attenuation is an exclusive explanation for the redshift evolution of the observed spectral break. Copyright © 2018, The Authors. All rights reserved.

关键词： Regression analysis

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SPECTRAL PROPERTIES OF MAGNETOHYDRODNAMIC TURBULENCE REVEALED BY POLARIZATION SYNCHROTRON EMISSION WITH FARADAY ROTATION

arXiv

引用

arXiv 2018年

作者： Zhang, Jian-Fu Lazarian, Alex Xiang, Fu-Yuan Department of Physics Xiangtan University Xiangtan Hunan411105 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Astronomy Department University of Wisconsin MadisonWI53711 United States

We investigate how to recover the spectral properties of underlying magnetohydrodynamic (MHD) turbulence using fluctuation statistics of synchrotron polarization radiation, based on the synthetic observations. Taking spatially coincident, separated, and compounded synchrotron emission and Faraday rotation regions into account, we extract the power spectrum of synchrotron polarization intensities integrated along the line of sight. Our results demonstrate that in the short wavelength range, the power spectra reflect fluctuation statistics of the perpendicular component of turbulent magnetic fields, and the spectra at long wavelengths reveal the fluctuation of the Faraday rotation density, which is a product of the parallel component of magnetic field and thermal electron density. We find that our numerical results (in the case of spatially coincident regions) are in agreement with the analytical prediction in Lazarian & Pogosyan (2016), and this theoretical prediction is applicable to more complicated settings, i.e., the spatially separated and compounded regions. We simulate telescopic observations that incorporate the effects of telescope angular resolution and noise, and find that statistics of underlying MHD turbulence can be recovered successfully. We expect that the technique can be applied to a variety of astrophysical environments, with existing synchrotron data cubes and a large number of forthcoming data sets from such as the LOw-Frequency Array for Radio astronomy (LOFAR), the Square Kilometer Array (SKA) and the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Copyright © 2018, The Authors. All rights reserved.

关键词： Power spectrum

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Optical multi-color monitoring of OJ 287 from 2006 to 2012

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Research in Astronomy and Astrophysics 2017年第8期17卷 57-68页

作者： Qian Guo Ding-Rong Xiong Jin-Ming Bai Xu-Liang Fan Wei-Min Yi Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100012 China University of Chinese Academy of Sciences Beijing 100049 China

We present our optical multi-color monitoring of the BL Lac object OJ 287 from January 2006to December 2012 in the V,R and I bands.A relatively active state in OJ 287 has been found over all monitored epochs,among which the variations of average magnitude in V/R/I bands were measured with ?V=1.956 mag,?R=2.067 mag and ?I=2.115 mag,*** reliable intraday variability is detected,but possible variability is detected on 16 *** relative variation amplitudes fall into the range between 1% and 8%,with the majority between 2% and 4%.No time lags have been detected,but strong correlations exist among light curves in the three *** bluer-when-brighter trend is dominant over intraday timescales,which supports the shock-in-jet *** combining with additional V/R band data obtained from SMARTS and the Steward Observatory,we also find a bluer-when-brighter trend over a long-term *** possible periods of 513,176,36,30,26,17 and 14 d are found in all time-series data sets from 2006 to *** explanations about these periods are given.

关键词： BL Lacertae objects individual(OJ 287)—galaxies active—galaxies photometry

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Physical properties and catalog of EW-type eclipsing binaries observed byLAMOST

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Research in Astronomy and Astrophysics 2017年第8期17卷 109-122页

作者： Sheng-Bang Qian Jia-Jia He Jia Zhang Li-Ying Zhu Xiang-Dong Shi Er-Gang Zhao Xiao Zhou Yunnan Observatories Chinese Academy of Sciences Kunming 650011 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100012 China University of the Chinese Academy of Sciences Beijing 100049 China

EW-type eclipsing binaries(hereafter called EWs)are strong interacting systems in which both component stars usually fill their critical Roche lobes and share a common *** EWs were discovered by several deep photometric surveys and there were about 40 785 EW-type binary systems listed in the international variable star index(VSX)by 2017 March 13.7938 of them were observed with LAMOST by 2016 November 30 and their spectral types were *** atmospheric parameters of 5363 EW-type binary stars were determined based on good spectroscopic *** the paper,those EWs are cataloged and their properties are *** distributions of orbital period(P),effective temperature(T),gravitational acceleration(log(g)),metallicity([Fe/H])and radial velocity(RV)are presented for these observed EW-type *** is shown that about 80.6% of sample stars have metallicity below zero,indicating that EW-type systems are old stellar *** is in agreement with the conclusion that EW binaries are formed from moderately close binaries through angular momentum loss via magnetic braking that takes a few hundred million to a few billion *** unusually high metallicities of a few percent of EWs may be caused by contamination of material from the evolution of unseen neutron stars or black holes in the *** correlations between orbital period and effective temperature,gravitational acceleration and metallicity are presented and their scatters are mainly caused by(i)the presence of third bodies and(ii)sometimes wrongly determined *** is shown that some EWs contain evolved component stars and the physical properties of EWs mainly depend on their orbital *** is found that extremely short-period EWs may be older than their long-period cousins because they have lower *** reveals that they have a longer timescale of pre-contact evolution and their formation and evolution are mainly driven by angular momentum loss vi

关键词： stars binaries close—stars binaries spectroscopic—stars binaries eclipsing—stars evolution

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Can Helium-detonation model explain the observed diversity of type Ia supernovae?

arXiv

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arXiv 2020年

作者： Li, Wenxiong Wang, Xiaofeng Bulla, Mattia Pan, Yen-Chen Wang, Lifan Mo, Jun Zhang, Jujia Wu, Chengyuan Zhang, Jicheng Zhang, Tianmeng Xiang, Danfeng Lin, Han Sai, Hanna Zhang, Xinghan Chen, Zhihao Yan, Shengyu Tsinghua University Beijing100084 China School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel Beijing Planetarium Beijing Academy of Science and Technology Beijing100089 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing210023 China Nordita KTH Royal Institute of Technology Stockholm University Roslagstullsbacken 23 Stockholm106 91 Sweden Graduate Institute of Astronomy National Central University 300 Jhongda Road Zhongli Taoyuan32001 Taiwan George P. and Cynthia Woods Mitchell Institute for Fundamental Physics & Astronomy Texas A. & M. University Department of Physics and Astronomy 4242 TAMU College StationTX77843 United States Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing10101 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China

We study a sample of 16 Type Ia supernovae (SNe Ia) having both spectroscopic and photometric observations within 2 − 3 days after the first light. The early B − V colors of such a sample tends to show a continuous distribution. For objects with normal ejecta velocity (NV), the C II λ6580 feature is always visible in the early spectra while it is absent or very weak in the high-velocity (HV) counterpart. Moreover, the velocities of the detached high-velocity features (HVFs) of Ca II NIR triplet (CaIR3) above the photosphere are found to be much higher in HV objects than in NV objects, with typical values exceeding 30,000 km s−1 at 2 − 3 days. We further analyze the relation between the velocity shift of late-time [Fe II] lines (v[Fe II]) and host galaxy mass. We find that all HV objects have redshifted v[Fe II] while NV objects have both blue- and redshifted v[Fe II]. It is interesting to point out that the objects with redshifted v[Fe II] are all located in massive galaxies, implying that HV and a portion of NV objects may have similar progenitor metallicities and explosion mechanisms. We propose that, with a geometric/projected effect, the He-detonation model may account for the similarity in birthplace environment and the differences seen in some SNe Ia, including B − V colors, C II feature, CaIR3 HVFs at early time and v[Fe II] in the nebular phase. Nevertheless, some features predicted by He-detonation simulation, such as the rapidly decreasing light curve, deviate from the observations, and some NV objects with blueshifted nebular v[Fe II] may involve other explosion mechanisms. © 2020, CC-BY.

关键词： Velocity

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Constraining the Rastall parameters in static spacetimes with galaxy-scale strong gravitational lensing

arXiv

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arXiv 2019年

作者： Li, Rui Wang, Jiancheng Xu, Zhaoyi Guo, Xiaotong Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China School of Astronomy and Space Science Nanjing University Nanjing Jiangsu210093 China

Recently, Rastall gravity is undergoing a significant surge in popularity. We obtain a power-law total mass-density profile for the inner region (within several effective radius) of early-type galaxies (ETGs) from the space-time structures which are described by the static spherically-symmetric solutions of Rastall gravity under the assumption of perfect fluid matter. We find that in the inner region of ETGs, the Rastall dimensionless parameter β = κλ determines the mass distribution. We then use 118 galaxy-galaxy strong gravitational lensing systems to constrain the Rastall dimensionless parameter β. We find that the mean value of β for total 118 ETGs is β = 0.163 ± 0.001(68% CL) with a minor intrinsic scatter of δ = 0.020 ± 0.001. Our work observationally illustrates the physical meaning of the Rastall dimensionless parameter in galaxy scale. From the Newtonian approximation of Rastall gravity, we also find that an absolute isothermal mass distribution for ETGs is not allowed in the framework of Rastall gravity. Copyright © 2019, The Authors. All rights reserved.

关键词： Galaxies

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The surviving companions in type Ia supernova remnants

引用

Research in Astronomy and Astrophysics 2017年第8期17卷 69-80页

作者： li-qing chen xiang-cun meng zhan-wen han yunnan observatories chinese academy of scienceskunming 650216china key laboratory for the structure and evolution of celestial objects chinese academy of scienceskunming 650216china university of chinese academy of sciences beijing 100049china center for astronomical mega-science chinese academy of sciencesbeijing 100012china

The single-degenerate(SD)model is one of the most popular progenitor models of type Ia supernovae(SNe Ia),in which the companion star can survive after an SN Ia explosion and show peculiar ***,searching for the surviving companion in type Ia supernova remnants(SNRs)is a potential method to verify the SD *** the SN 1604 remnant(Kepler’s SNR),although Chandra X-ray observation suggests that the progenitor is most likely a WD+AGB system,the surviving companion has not been *** possible reason is rapid rotation of the white dwarf(WD),causing explosion of the WD to be delayed for a spin-down timescale,and then the companion evolved into a WD before the supernova explosion,so the companion is too dim to be *** aim to verify this possible explanation by carrying out binary evolution *** this paper,we use Eggleton’s stellar evolution code to calculate the evolution of binaries consisting of a WD+red giant(RG).We assume that the rapidly rotating WD can continuously increase its mass when its mass exceeds the Chandrasekhar mass limit(MCh=1.378 M_⊙)until the mass-transfer rate decreases to be lower than a critical ***,we obtain the final masses of a WD in the range 1.378 M_⊙ to 2.707 M_⊙.We also show that if the spin-down time is less than 10~6yr,the companion star will be very bright and easily observed;but if the spin-down time is as long as^10~7 yr,the luminosities of the surviving companion would be lower than the detection *** simulation provides guidance in hunting for the surviving companion stars in SNRs,and the fact that no surviving companion has been found in Kepler’s SNR may not be definite evidence disfavoring the SD origin of Kepler’s SN.

关键词： stars evolution—binaries symbiotic—supernovae individual(SN 1604,SN 1006)

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